Mutual Fund Survivorship

This article provides a comprehensive study of survivorshipissues using the mutual fund data of Carhart (1997). We demonstratetheoretically that when survival depends on multiperiod performance,the survivorship bias in average performance typically increaseswith the sample length. This is empirically relevant becauseevidence suggests a multiyear survival rule for U.S. mutualfunds. In the data we find the annual bias increases from 0.07%for 1-year samples to 1% for samples longer than 15 years. Wefind that survivor conditioning weakens evidence of performancepersistence. Finally, we explain how survivor conditioning affectsthe relation between performance and fund characteristics.     

Improving the productivity of vertisols in the Accra plains of Ghana using leguminous cover crops

The productivity of the Vertisols of the Accra plains is low, in spite of its high potential fertility. This could be attributed to physical constraints and low organic matter content. A study was conducted at the Agricultural Research Centre, Kpong, to assess the suitability of Mucuna pruriens, Mimosa invisa and Stylosanthes guianensis, in short fallows, for improving the fertility, physical properties, moisture conservation and weed control in the case of these soils. Mucuna had the highest biomass of 5.3tha^?1, as opposed to 4.1tha^?1 under natural fallow. The mucuna and stylosanthes biomass had comparatively higher total N values (240.75 and 203.51kgha^?1, respectively) than mimosa and natural fallow (152.46 and 162.74kgha^?1, respectively). Soil organic carbon, one year after the incorporation of cover crops, was found to be relatively higher under the cover crops (mucuna, stylosanthes and mimosa) than it was under natural fallow. Bulk densities were thus lower under the cover crops than they were under natural fallow. Also, soils under the cover crops had higher total porosity, water infiltration rates and moisture storage than they did under natural fallow. Weed cover, 115 days after planting maize, was significantly lower in plots previously under Mucuna pruriens than it was under natural fallow, Stylosanthes guianensis and Mimosa invisa. There was a negative linear correlation between cover crop biomass and weed density (R ² = 0.593–0.805). Grain and stover yields of maize were higher under Mucuna pruriens than they were under natural fallow (138 and 70 per cent higher, respectively). Burning of the natural fallow resulted in greater weed growth than when the material was worked into the soil (41 and 8 per cent, respectively). Grain yield was significantly greater under mucuna than it was under natural fallow (3.1 and 1.3tha^?1, respectively).     

Cost-effectiveness of stent-retriever thrombectomy in combination with IV t-PA compared with IV t-PA alone for acute ischemic stroke in the UK

Objective: To evaluate the cost-effectiveness of neurothrombectomy with a stent retriever (Solitaire**Solitaire Revascularization Device is a registered trademark of Medtronic (Irvine, CA).View all notes Revascularization Device) in treating acute ischemic stroke patients from the UK healthcare provider perspective.

Methods: A Markov model was developed to simulate health outcomes and costs of two therapies over a lifetime time horizon: stent-retriever thrombectomy in combination with intravenous tissue-type plasminogen activator (IV t-PA), and IV t-PA alone. The model incorporated an acute phase (0–90 days) and a rest of life phase (90+ days). Health states were defined by the modified Rankin Scale score. During the rest of life phase, patients remained in the same health state until a recurrent stroke or death. Clinical effectiveness and safety data were taken from the SWIFT PRIME study. Resource use and health state utilities were informed by published data.

Results: Combined stent-retriever thrombectomy and IV t-PA led to improved quality-of-life and increased life expectancy compared to IV t-PA alone. The higher treatment costs associated with the use of stent-retriever thrombectomy were offset by long-term cost savings due to improved patient health status, leading to overall cost savings of £33 190 per patient and a net benefit of £79 402. Deterministic and probabilistic sensitivity analyses demonstrated that the results were robust to a wide range of parameter inputs.

Limitations: The acute and long-term costs resource use data were taken from a study based on a patient population that was older and may have had additional comorbidities than the SWIFT PRIME population, resulting in costs that may not be representative of the cohort within this model. In addition, the estimates may not reflect stroke care today as no current evidence is available; however, the cost estimates were deemed reasonable by clinical opinion.

Conclusions: Combined stent-retriever neurothrombectomy and IV t-PA is a cost-effective treatment for acute ischemic stroke compared with IV t-PA alone.     

Discount rates for long-term projects: the cost of capital and social discount rate compared

Research on the cost of capital and on the social discount rate (SDR) has developed largely along separate paths. This paper offers an overview and comparison of both concepts. The consumption-based theory of discount rates is common to both, but there are striking differences in how the cost of capital and SDR are estimated. A project's cost of capital is inferred in practice from market data, by a well-established package of techniques, and project risk makes a large difference. In contrast, the SDR is estimated by applying judgement about the welfare of future generations, in the setting of consumption-based theory. Project risk has tended to be ignored under the SDR approach.     

Sexual orientation,work, and income in Canada

Abstract. We provide the first evidence on sexual orientation and economic outcomes in Canada using confidential data that ask adults a direct question about their sexual orientation. Gay men have 12% lower personal incomes and lesbians have 15% higher personal incomes than otherwise similar heterosexual men and women, respectively. Different labour force patterns can account for some of the income differentials. We also document large differences in educational attainment, childrearing, and urbanicity that generally mirror patterns found in the US. Finally, we show that applying couples‐based approaches common in this literature greatly overstates the magnitudes of gay/straight income gaps.     

Is Occupational Injury Risk Higher at New Firms?*

This paper studies whether newly created firms have higher injury rates than established firms. We use data on a large sample of single‐establishment firms in Pennsylvania from 2001–2005 to examine the relationship between firm age and the risk of lost workday injuries. Using the full set of firms, there appears to be little overall correlation between firm age and risk. If anything, newer firms appear less likely to have lost workday injuries. When we condition on having at least one injury reported in 2000, however, we find that in later years the injury risk of firms declines with age. This pattern is consistent with systematic underreporting of injuries by new firms.     

The elusive relation between pension discount rates and deficits

The relation between defined-benefit (DB) pension discount rates and funding status is more complex than it might first appear. Existing evidence suffers from estimation biases that make precise inference unreliable. We document the biases and quantify their impact on inference in relation to corporate window-dressing of DB funding status. Our empirical evidence from the United Kingdom suggests that pension sponsors use discretion in the choice of pension discount rate not only to reduce reported deficits but also to reduce reported surpluses.